Concrete face rockfill dams - Geotechnical Engineering of Dams - page 590

Table 15.1. Historical summary of the trend in design and rockfill compaction in CFRD and Earth and

Rockfill dams (Hunter 2003; Hunter and Fell 2002, based on Galloway 1939; Cooke 1984,
1993).

Approximate Method of placement and

time period characteristics of rockfill Comments

Concrete faced rockfill dams
Mid to late 1800s Dumped rockfill with timber facing Early embankments constructed with

to early 1900s timber facing. Typically of very steep

slopes (up to 0.5 to 0.75 H to 1 V).
First usage of concrete facing in the
1890s. Height limited to about 25 m.

1920s-1930s Dumped in high lifts (up to 20 to Rockfill typically sound and not

50 m) and sluiced, hand or derrick subject to disintegration. Dam heights

placed upstream rockfill zone. reaching 80 to 100 m. For high dams

Sluicing relatively ineffective cracking of facing slab and joint

openings resulted in high leakage
rates (2700 l/sec Dix River, 3600 l/sec
Cogswell, 570 l/sec Salt Springs).

Late 1930s High pressure sluicing used. Cracking of face slab, particularly

to 1960s Rockfill still very coarse at the perimeter joint, and high leakage

rates a significant issue with higher
dams (3100 l/sec at Wishon,
1300 l/sec at Courtright).

From late 1960s Rockfill placed in 1-2 m lifts, Significant reduction in

watered and compacted. Reduction post-construction deformations due

in particle size. Usage of gravels to low compressibility of compacted

and lower strength rock rockfill. Significant reduction in leakage

rates; maximum rates typically
less than 50-100l/sec. Continued
improvement in plinth design
and facing details to reduce
cracking and leakage.

Earth and rockfill dams
1900 to 1930 Dumped rockfill Use of concrete cores with

dumped rockfill shoulders at
angle of repose. Limited use of
earth core. Dam heights
up to 50-70 m.

1930s to 1960s Earth core (sloping and central) Use of earth cores significant from

with dumped rockfill shoulders the 1940s due to the difficulties

with leakage of CFRD. Increasing
dam heights up to 150 m.

From 1960s Use of compacted rockfill. Improvements in compaction techniques.

Typically placed in 1-2 m lifts, Early dams compacted in relatively thick

watered and compacted with rollers layers with small rollers. Gradual

increase in roller size and reduction
in layer thickness reduced the
compressibility of the rockfill.
Significant increase in dam heights in
the mid to late 1970s, up to 250-300 m.

The dam consists of:
Plinth . Reinforced concrete slab cast on sound, low permeability rock to join the face
slab to the foundation.
Face slab . Reinforced concrete, preferably between 0.25 and 0.6 m thick, with vertical,
some horizontal and perimetric joints to accommodate deformation which occurs during
construction and when the water load is applied.